Tapu Bulu

Tapu Bulu has passable bulk to go with its Grass / Fairy typing, a decent movepool, and, most importantly, an excellent ability in Grassy Surge. It is able to tank some powerful hits, such as an Fake Out followed by Giga Impact from Mega Lopunny and Shattered Psyche from Tapu Lele, under Grassy Terrain. Tapu Bulu's Grass typing matches it up very well against Mega Gyarados, a very formidable and prevalent threat. It is also the slowest of all the Guardian Deities, which means that its Terrain activates the latest on the field and prevails for the first five turns of the battle. However, the absence of a good physical Fairy-type STAB move and a weakness to commonly used types like Fire, Flying, and Steel present major drawbacks to its usage. Its typing causes it to be easily KOed by Pokemon like Mega Charizard X, Flyinium Z Dragonite, and Mega Metagross. It also has a subpar Speed stat and just decent Special Defense. This leaves Tapu Bulu vulnerable to powerful special attacks like Porygon-Z's Hyper Beam and Choice Specs Greninja's Ice Beam before it gets the chance to land a hit on these Pokemon.